1. Field
Example embodiments herein relate to a semi-permeable film and a separation membrane including a nanoporous material, and a method of manufacturing the same.
2. Description of the Related Art
To acquire fresh water or gray water from sea water or sewage and waste water, suspended or dissolved components should be removed in conformity with the standards for drinking water. At present, reverse osmosis is conventionally used as a water treatment method for desalinating or making gray water out of sea water or sewage and waste water.
According to the water treatment method using a reverse osmotic membrane, a pressure corresponding to an osmotic pressure caused by dissolved components is applied to the raw water to separate a dissolved component, such as a salt (NaCl), from water. For example, the concentration of the salt dissolved in sea water ranges from about 30,000 to about 45,000 ppm and the osmotic pressure caused from the concentration ranges from about 20 atm to about 30 atm. As a result, a pressure of about 20 atm to about 30 atm or higher is applied to the raw water to produce fresh water from the raw water. Generally, energy in the amount of about 6 kW/m3 to about 10 kW/m3 is required to produce about 1 m3 of fresh water from sea water.
Recently, an energy recollection device has been developed and applied in an attempt to save the energy consumed during a reverse osmosis process. However, in this case, about 3 kW/m3 of energy is still required to drive a motor of a high-pressure pump.
To resolve the problem, a water treatment process using a forward osmosis separation membrane has been suggested as an alternative. The forward osmosis process is relatively economical compared with the reverse osmosis process, because the forward osmosis process does not require pressure but uses a natural osmosis phenomenon. As a result, researchers have been studying the development of the forward osmosis separation membrane.
Researchers tried to improve a salt rejection rate and an elution rate (or a permeation flux) by introducing inorganic particles into the separation membrane during the reverse osmosis or forward osmosis process. Although the introduction of the inorganic particle may improve the elution rate, the salt rejection rate is decreased, thus serving as a restrictive factor.